Motor vehicle equipment is incorporating an increasing number of control members for controlling functional members of such vehicles.
Several pieces of equipment placed in a vehicle cabin receive control members of this type which are thus made available to users of the vehicle.
By way of example, these pieces of equipment can be constituted by door panels, the dashboard, or indeed a central console of the vehicle, etc. . . . .
In general, the control members are grouped together to make up control pads made up of various kinds of member, such as, for example: switches, pushbuttons, or knobs for turning, which members are integrated in the electrical control circuits for the functional members.
However, it will be understood that such members present certain drawbacks, in particular concerning their bulkiness and their lack of reliability, particularly since they make use of moving parts.
Another problem associated with using members of that type lies in the complexity of assembling them and installing them on board the vehicle which requires the use of assembly components (screws, a pad support plate, etc. . . . ) and assembly time that is relatively lengthy.
Touch-sensitive detectors are themselves also known in general terms.
Reference can be made for example to the following documents: FR-A-2 779 889, FR-A-2 737 359, U.S. Pat. No. 5,572,205, and U.S. Pat. No. 5,270,710.
Such detectors operate on the principle of detecting a change in capacitance, for example by means of an electrode placed on a printed circuit board under a zone for operating a control, with said change in capacitance subsequently being analyzed and processed by an electronic circuit that serves to control some function. Beneath a predetermined capacitance threshold, a control signal is not generated, and above the threshold, a control signal is generated.
Such detectors present the advantage of not requiring moving parts, but they suffer from a drawback of lack of feedback to the user, in particular in terms of feel.
Thus, for example, with a touch-sensitive system, such as that described in document U.S. Pat. No. 5,572,205, in which a rigid support is provided with a capacitive sensor on one face of the support and an operating zone in register therewith on the other face of the support, the user perceives no sensation of pressing on a button.
This can be troublesome, for example if the user is the driver of the vehicle and is pressing the control members “blind”.
Without any tactile feedback, the user can end up pressing several times on the operation zone and runs the risk of not obtaining the desired effect.
Furthermore, this also leads to a problem of lack of concentration on driving the vehicle.
Document U.S. Pat. No. 4,022,296 describes a control unit having capacitive control switches which likewise give rise to such problems.
Document EP-02/290167.2 in the name of the Applicant describes a capacitive type control member for controlling at least one functional member, in particular of a motor vehicle, the control member comprising a rigid support structure, at least one capacitive cell for detecting touch and located on or close to one of the faces of said support structure, and at least one control operation zone located on or close to the other face of said support structure in register with the touch detection capacitive cell, the control operation zone comprising elastically deformable means. Thus, the user can feel displacement when pressing the operation zone. The perception of operating a control is thus greatly improved. In one embodiment, the elastically deformable means have a rest position in which the finger of the operator in contact with the operation zone lies outside the touch detection space, and a deformed position in which the finger of the operator in contact with the operation zone lies within the touch detection space. This characteristic makes it possible to monitor triggering of the control more securely by constraining the user to depress the operation zone in order to enter the touch detection space. The term “touch detection space” is used to mean the space in which the operator's finger causes a change in capacitance that goes beyond the predetermined capacitance threshold, thereby causing a control signal to be generated.